Conventionally, there has been proposed a linear motor used in factory automation equipments to drive a stage of a semiconductor exposure device or a liquid crystal exposure device or to feed a table of a machine tool. In order to achieve an increase in speed and accuracy of feeding or processing operations, the linear motor includes permanent magnets making up a field magnet, and an armature having armature windings facing the magnetic pole surfaces of the permanent magnet in a magnetic space.
The armature of the linear motor includes armature windings, a base plate for positioning and fixing the armature windings in place, a frame for fixing the base plate in place and a cover for sealing the frame. The frame includes a large coolant pool formed in the central area thereof. The armature windings are accommodated within the coolant pool. The side surfaces of the coolant pool are sealed by the cover. The frame is provided with a coolant inlet and a coolant outlet. Within the core of the frame, there are formed a coolant incoming path and a coolant outgoing path, which communicate with the coolant inlet and the coolant outlet, respectively (see, e.g., Japanese Patent Application Publication No. 2006-121813).